-
Applied Superconductivity, IEEE Transactions on. 01/2013; PP(99):1-1.
-
-
[show abstract]
[hide abstract]
ABSTRACT: The anisotropic irreversibility field B$_{Irr}$ of two $YBa_2Cu_3O_{7-x}$
thin films doped with additional rare earth (RE)=(Gd,Y) and Zr and containing
strong correlated pins (splayed BaZrO$_{3}$ nanorods, and $RE_2O_3$
nanoprecipitates), has been measured over a very broad range up to 45T at
temperatures 56 K<T<$T_c$. We found that the experimental angular dependence of
$B_{Irr}(\theta)$ does not follow the mass anisotropy scaling
$B_{Irr}(\theta)=B_{Irr}(0)(cos^2\theta+\gamma^{-2}sin^2\theta)^{-1/2}$, where
$\gamma=(m_c/m_{ab})^{1/2}=5-6$ for the RE-doped $YBa_2Cu_3O_{7-x}$ (REBCO)
crystals, m$_{ab}$ and m$_{c}$ are the effective masses along the ab plane and
the c-axis, respectively, and $\theta$ is the angle between B and the c-axis.
For B parallel to the ab-planes and to the c-axis correlated pinning strongly
enhances B$_{Irr}$, while at intermediate angles, $B_{Irr}(\theta)$ follows the
scaling behavior
$B_{Irr}(\theta)\propto(cos^2\theta+\gamma_{RP}^2sin^2\theta)^{1/2}$ with the
effective anisotropy factor $\gamma_{RP}\approx3$ significantly smaller than
the mass anisotropy would suggest. In spite of the strong effects of c-axis
BaZrO$_{3}$ nanorods, we found even greater enhancements of B$_{Irr}$ for
fields along the ab-planes than for fields parallel to the c-axis, as well as
different temperature dependences of the correlated pinning contributions to
B$_{Irr}$ for B//ab and B//c. Our results show that the dense and strong pins,
which can now be incorporated into REBCO thin films in a controlled way, exert
major and diverse effects on the measured vortex pinning anisotropy and the
irreversibility field over wide ranges of B and T. In particular, we show that
the relative contribution of correlated pinning to B$_{Irr}$ for B//c increases
as the temperature increases due to the suppression of thermal fluctuations of
vortices by splayed distribution of BaZrO$_{3}$ nanorods.
01/2012;
-
Physics Procedia 01/2012; 36:582-587.
-
[show abstract]
[hide abstract]
ABSTRACT: Large-scale, high-rate epitaxial growth technology for the second-generation superconducting wire brings unique technological challenges for the thin-film coating industry. One of the most difficult steps of the process is controlling nucleation of a complex compound over a km-long low-cost oxide template. Here, we analyze early stages of industrial-scale epitaxial metal organic chemical vapor deposition (MOCVD) growth of ReBa2Cu3Ox (REBCO, Re = rare-earth) on buffered metal substrates. The nucleation event is detected by high-flux synchrotron X-ray diffraction and confirmed by atomic force microscopy. REBCO nuclei exhibit a strong preference for edges of the buffer grain, indicating that (001) steps of the buffer grains are preferred nucleation sites. It is concluded that random nucleation of REBCO is caused by agglomerates of small buffer grains.
Journal of Applied Physics 12/2011; 110(12):123904-123904-6. · 2.17 Impact Factor
-
V. Selvamanickam, Y. Chen,
I. Kesgin,
A. Guevara,
T. Shi,
Y. Yao,
Y. Qiao,
Y. Zhang,
G. Majkic,
G. Carota,
A. Rar,
Y. Xie,
J. Dackow,
B. Maiorov,
L. Civale,
V. Braccini,
J. Jaroszynski,
A. Xu,
D. Larbalestier,
R. Bhattacharya
[show abstract]
[hide abstract]
ABSTRACT: Second-generation (2G) HTS wires are now being produced routinely in kilometer lengths using Metal Organic Chemical Vapor Deposition (MOCVD) process with critical currents of 300 A/cm. While this achievement is enabling several prototype devices, in order to reach a substantial commercial market, the cost-performance metrics of 2G HTS wires need to be significantly improved in device operating conditions. Zr-doping has been found to be an effective approach to improve in-field critical current performance of MOCVD-based HTS wires. In this work, we have explored modifications to the Zr-doped precursor compositions to achieve three and two-fold increase in deposition rate in research and production MOCVD systems respectively. Production wires made with modified Zr-doped compositions exhibit a self-field critical current density of 50 MA/cm<sup>2</sup> at 4.2 K and a 55 to 65% higher performance than our previous wires with Zr-doping, over magnetic field range of 0 to 30 T. We have also developed an alternate, low-cost technique, namely electrodeposition, to deposit silver overlayer on superconducting film. Wires made with electrodeposited silver are able to sustain the same level of overcurrent as sputtered silver layers. This process has been successfully scaled up to 100 m lengths.
IEEE Transactions on Appiled Superconductivity 07/2011; · 1.04 Impact Factor
-
V. Braccini,
A Xu,
J. Jaroszynski,
Y Xin,
D. C. Larbalestier, Y Chen,
G. Carota,
J Dackow,
I Kesgin,
Y Yao,
A Guevara,
T Shi,
V. Selvamanickam
[show abstract]
[hide abstract]
ABSTRACT: BaZrO3 (BZO) nanorods are now incorporated into production IBAD-MOCVD coated conductors. Here we compare several examples of both BZO-free and BZO-containing coated conductors using critical current (Ic) characterizations at 4.2 K over their full angular range up to fields of 31 T. We find that BZO nanorods do not produce any c-axis distortion of the critical current density Jc(theta) curve at 4.2 K at any field, but also that pinning is nevertheless strongly enhanced compared to the non-BZO conductors. We also find that the tendency of the ab-plane Jc(theta) peak to become cusp-like is moderated by BZO and we define a new figure of merit that may be helpful for magnet design - the OADI (Off-Axis Double Ic), which clearly shows that BZO broadens the ab-plane peak and thus raises Jc 5-30{\deg} away from the tape plane, where the most critical approach to Ic occurs in many coil designs. We describe some experimental procedures that may make critical current Ic tests of these very high current tapes more tractable at 4.2 K, where Ic exceeds 1000 A even for 4 mm wide tape with only 1 micron thickness of superconductor. A positive conclusion is that BZO is very beneficial for the Jc characteristics at 4.2 K, just as it is at higher temperatures, where the correlated c-axis pinning effects of the nanorods are much more obvious.
11/2010;
-
V Selvamanickam,
A Guevara,
Y Zhang,
I Kesgin,
Y Xie,
G Carota, Y Chen,
J Dackow,
Y Zuev,
C Cantoni,
A Goyal,
J Coulter,
L Civale
[show abstract]
[hide abstract]
ABSTRACT: The influence of Zr doping in (Gd, Y)–Ba–Cu–O ((Gd, Y)BCO) tapes made by metal–organic chemical vapor deposition has been studied with a specific objective of uniform and reproducible enhancement in in-field critical current (Ic) over long lengths. 50 m long tapes with 7.5 and 10 at.% Zr doping in 1 µm thick (Gd, Y)BCO films have been found to exhibit a sharply enhanced peak in Ic in the orientation of field parallel to the c-axis and retain 28% of their self-field Ic value at 77 K and 1 T. BaZrO3 (BZO) nanocolumn density in the cross-sectional microstructure was found to increase with increasing Zr addition. The end segments of the 50 m long tapes were found to display nearly identical angular dependence of critical current at 77 K and 1 T, indicative of the uniformity in in-field performance over this length. A 610 m long tape was fabricated with 10% Zr doping and a 130 m segment showed a 3.2% uniformity in critical current measured every meter in the orientation of -axis. A retention factor of 36% of the zero-field Ic value measured at 0.52 T over the 130 m is consistent with that obtained in short samples.
Superconductor Science and Technology 12/2009; 23(1):014014. · 2.66 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We present very high field angle dependent critical current density (Jc) data for three recently obtained YBa2Cu3O7−x (YBCO) coated conductors used in the construction of high field solenoids. We find that strongly correlated pins, such as BaZrO3 (BZO) nanorods, while yielding strong c-axis peaks at 77 K, produce almost no measurable contribution at 4 K. Raising the field from <5 to 30 T at 4 K causes a marked transition from a Ginzburg–Landau-like Jc(θ) at low fields to a marked cusp-like behavior at high fields. Transmission electron micrographs show that all samples contain a high density of stacking faults which strengthen the plane correlated pinning parallel to the ab planes produced by the intrinsic ab-plane pinning of the Cu–O charge reservoir layers.
Superconductor Science and Technology 12/2009; 23(1):014003. · 2.66 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We have made extensive low temperature and high field evaluations of a recent 2.1 µm thick coated conductor (CC) grown by metal–organic chemical vapor deposition (MOCVD) with a view to its use for high field magnet applications, for which its very strong Hastelloy substrate makes it very suitable. This conductor contains dense three-dimensional (Y,Sm)2O3 nanoprecipitates, which are self-aligned in planes tilted ~7° from the tape plane. Very strong vortex pinning is evidenced by high critical current density Jc values of ~3.1 MA cm−2 at 77 K and ~43 MA cm−2 at 4.2 K, and by a strongly enhanced irreversibility field Hirr, which reaches that of Nb3Sn (~28 T at 1.5 K) at 60 K, even in the inferior direction of axis. At 4.2 K, Jc values are ~15% of the depairing current density Jd, much the highest of any superconductor suitable for magnet construction.
Superconductor Science and Technology 04/2009; 22(5):055013. · 2.66 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: (Gd,Y)Ba(2)Cu(3)O(x) tapes have been fabricated by metal organic chemical vapor deposition (MOCVD) with Zr-doping levels of 0-15 mol.% and Cc doping levels of 0-10 mol.% in 0.4 mu m thick films. The critical current density (J(c)) of Zr-doped samples at 77 K, 1 T applied in the orientation of H parallel to c is found to increase with Zr content and shows a maximum at 7.5% Zr doping. The 7.5% Zr-doped sample exhibits a critical current density (J(c)) of 0.95 MA/cm(2) at H parallel to c which is more than 70% higher than the J(c) of the undoped sample. The peak in Jc at H parallel to c is 83% of that at H parallel to a-b in the 7.5% Zr-doped sample which is more than twice as that in the undoped sample. Superconducting transition temperature (T(c)) values as high as about 89 K have been achieved in samples even with 15% Zr and 10% Ce. Ce-doped samples with and without Ba compensation are found to exhibit substantially different J(c) values as well as angular dependence characteristics. (C) 2009 Elsevier B.V. All rights reserved.
Physica C-Superconductivity and Its Applications. 01/2009; 469(23-24):2037-2043.
-
[show abstract]
[hide abstract]
ABSTRACT: The anisotropic irreversibility field BIrr of two YBa2Cu3O7−x thin films doped with additional rare earth (RE) = (Gd, Y) and Zr and containing strong correlated pins (splayed BaZrO3 nanorods and RE2O3 nanoprecipitates) has been measured over a very broad range up to 45 T at temperatures 56 K < T < Tc. We found that the experimental angular dependence of BIrr (θ) does not follow the mass anisotropy scaling BIrr(θ)=BIrr(0)(cos2θ+γ−2 sin2θ)−1/2, where γ=(mc/mab)1/2=5−6 for the RE-doped YBa2Cu3O7−x (REBCO) crystals, mab and mc are the effective masses along the ab plane and the c-axis, respectively, and θ is the angle between B and the c-axis. For B parallel to the ab planes and to the c-axis correlated pinning strongly enhances BIrr, while at intermediate angles, BIrr(θ) follows the scaling behavior BIrr(θ)∝(cos2θ+γRP−2 sin2θ)−1/2 with the effective anisotropy factor γRP≈3 significantly smaller than the mass anisotropy would suggest. In spite of the strong effects of c-axis BaZrO3 nanorods, we found even greater enhancements of BIrr for fields along the ab planes than for fields parallel to the c-axis, as well as different temperature dependences of the correlated pinning contributions to BIrr for B//ab and B//c. Our results show that the dense and strong pins, which can now be incorporated into REBCO thin films in a controlled way, exert major and diverse effects on the measured vortex pinning anisotropy and the irreversibility field over wide ranges of B and T. In particular, we show that the relative contribution of correlated pinning to BIrr for B//c increases as the temperature increases due to the suppression of thermal fluctuations of vortices by splayed distribution of BaZrO3 nanorods.
Phys. Rev. B. 84(22).
